There are already many techniques for keeping the flatness of a surface highly even when decoration is added to a touch panel. For example, there is a method for laminating a decoration film on an operation surface.
FIG. 1A is a cross-section diagram of a resistive film type touch panel having no decoration film. FIG. 1B is a cross-section diagram of a resistive film type touch panel having a decoration film.
A resistive film type touch panel 1 of FIG. 1A includes: an upper transparent substrate 11 constituting an operation surface; an upper transparent electrode film 12 bonded to a lower surface of the upper transparent substrate 11; a lower transparent substrate 13 arranged at a lowest position; a lower transparent electrode film 14 bonded to an upper surface of the lower transparent substrate 13; and an electric wiring 15 provided between the upper transparent electrode film 12 and the lower transparent electrode film 14. An air gap 16 is formed between the upper transparent electrode film 12 and the lower transparent electrode film 14. A resistive film type touch panel 1′ of FIG. 1B includes a decoration film 17 in addition to the resistive film type touch panel 1 of FIG. 1A. The decoration film 17 is laminated on the upper transparent substrate 11.
In the case of the resistive film type touch panel 1 of FIG. 1A and the resistive film type touch panel 1′ of FIG. 1B, the upper transparent electrode film 12 needs to physically touch the lower transparent electrode film 14 to detect a position which a finger or a pen touches. Therefore, a certain degree of a load needs to be applied to the operation surface. Accordingly, in a method of laminating the decoration film 17 on the upper transparent substrate 11, as illustrated in FIG. 1B, the decoration film 17 is also overlapped with an operation area 18. Therefore, there occurs a problem that a load for input in accordance with hardness of the decoration film 17 increases.
To solve the problem, there is a method of providing a decoration layer 17A in the back of the operation surface (i.e., on the lower surface of the upper transparent electrode film 12), as illustrated in FIG. 2A. In this case, since the upper transparent electrode film 12 is not electrically conducted with the electric wiring 15, there occurs a problem that the touch panel does not work.
Therefore, there has been known a configuration in which a part of the electric wiring 15 is connected to the lower surface of the upper transparent electrode film 12 along a side surface of the decoration layer 17A, as illustrated in FIG. 2B (e.g. see Japanese Laid-open Patent Publication No. 2014-16857). Moreover, there has been known a configuration in which the decoration layer 17A is provided between the upper transparent substrate 11 and the upper transparent electrode film 12 (e.g. see Japanese Registered Utility Model No. 3167028).